Encoding voice pitch for profoundly hearing-impaired listeners.

The ability of five profoundly hearing-impaired subjects to "track" connected speech and to make judgments about the intonation and stress in spoken sentences was evaluated under a variety of auditory-visual conditions. These included speechreading alone, speechreading plus speech (low-pass filtered at 4 kHz), and speechreading plus a tone whose frequency, intensity, and temporal characteristics were matched to the speaker's fundamental frequency (F0). In addition, several frequency transfer functions were applied to the normal F0 range resulting in new ranges that were both transposed and expanded with respect to the original F0 range. Three of the five subjects were able to use several of the tonal representations of F0 nearly as well as speech to improve their speechreading rates and to make appropriate judgments concerning sentence intonation and stress. The remaining two subjects greatly improved their identification performance for intonation and stress patterns when expanded F0 signals were presented alone (i.e., without speechreading), but had difficulty integrating visual and auditory information at the connected discourse level, despite intensive training in the connected discourse tracking procedure lasting from 27.8-33.8 h.